


Bodies Change

by mabelsguidetolove



Category: Gravity Falls
Genre: Cunnilingus, F/M, Incest, Older Characters, Sibling Incest, Smut, Twincest, pinecest - Freeform, pinescest - Freeform
Language: English
Status: Completed
Published: 2016-02-21
Updated: 2016-02-21
Packaged: 2018-05-22 09:30:35
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,364
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6074082
Author URL: https://archiveofourown.org/users/mabelsguidetolove/pseuds/mabelsguidetolove
Summary: <blockquote class="userstuff">
              <p>A re-post of my first smut fic. Dip ‘n’ Mabes take a bath together for the first time since they were little kids. It gets steamy up in there.</p>
            </blockquote>





	Bodies Change

12:36. It was 12:36, and Dipper and Mabel Pines hadn’t gone to sleep yet. 

Not that they weren’t going to try; in fact, they were preparing to do just that presently. Mabel, of course, hopped in the bathtub before Dipper even got a chance to take dibs, so he was stuck placidly brushing his teeth until then. 

“Dip?” He suddenly heard his sister inquire through the blue paisley curtain that separated them, water running softly in the background. “Could you pass me that giant thing of bubble bath mom bought at the store yesterday? Because bubblegum scented bubbles sound perfect right about now.”

Dipper spat out the minty foam forming in his mouth to answer.

“Hmm? Oh, yeah.” And with that, he picked up the half gallon bottle of knockoff Mister Bubble from the floor. “Here.”

Then came a dilemma.

She wasn’t reaching out to take the container from his hand.

He cleared his throat.

“H-Here you go, Mabel.” He repeated awkwardly, scratching his slightly scruffy chin absentmindedly.

He had no idea what his sister had in store for him that night. Neither did she, particularly, but she had been harboring feelings for him a couple of weeks now, and this was her way of flirting. He probably wouldn’t be responsive to it, but it didn’t hurt for her to try, from what she could tell.

“Pour it for me.”

“What?!”

“Pour it for me, bro.” She repeated demandingly from inside the fortress of water and steam. “It’s not a problem, right?”

There was a silence. Was she really that tired? Dipper wondered. Did she seriously not know what that would mean?

He sighed. _Screw it, let’s get this over with._

Opening the curtain ever so slightly at the faucet end, he reached a hand into the humid entrenchment to test the water temperature. Not that it mattered, but he wanted to make sure his sister wasn’t too warm in there. Then, he poured the viscous pink liquid into the bath…

And was congratulated with a smooch on the cheek?

His sister jubilantly popped out from behind the shower curtain, splashing some water out of the tub in the process, and she immediately planted one on him.

“Muah! Thanks, Dipper!”

She cracked a mischievous, excited smile and looked him straight in the face. Dipper, however, seemed to be somewhat embarrassed. Distracted, almost.

Real distracted, actually.

“Uhh, Mabel? I—”

“What is it?You like what you see?” She said, smirking, not even looking away to stop the flow of the hot water which was now engulfing her.

Without the babbling noise of water hitting water, they were now encroached in a world of silence.

Dipper didn’t know what to say. After all, it’s hard to come up with a response when your sister asks you how attractive her naked body is. I mean, that’s just not normal, is it? And it was less normal to actually feel aroused at the situation he was currently in.

_Man, this is so messed up._

His sister came upon a sudden pang of reality. This was her brother. Of course he wouldn’t be into her body, no matter how naked and attractive it was.

“Oh my gosh. I’m sorry. Of course you don’t like it, do you?” She cringed, looking down at the water with a thousand yard stare of sadness and covering her chest.

“No, no, I like it. Definitely. It’s just, you know…”

“Right. I just forgot for a sec.”

More silence.

“Hey Dipper.”

“What?”

“Do you remember when we were little and we would take baths together?”

She leaned on the white porcelain wall of the tub, cradling her plush cheek with the crook of her elbow.

“Yeah.”

“Do you think we could do that again?”

“What, seriously?”

“Only if you’re up for it, I mean… I totally get it if you don’t want to, obviously.”

He assessed his surroundings. He was worn out, dirty and sweaty from the trials and tribulations the day had offered him. And that bath water, with its random puffs of white steam rising from the surface, really did look inviting. And there was such anticipation in his sister’s eyes…

“Why not?” He shrugged, beginning to toss his clothes to the ground hesitantly, but haphazardly. Meanwhile, Mabel’s face broke into an undisguised grin. 

After he was fully disrobed (much to his chagrin; Grunkle Stan was totally right when he said that bodies change), he slipped into the bath with his sister, feeling a little anxious about the choice he’d just made. After all, Mabel stealing glances at him the whole time he got in wasn’t making it any less weird.

For a few minutes, they sat across from one another, legs intertwined, trying as hard as possible not to look at each other for too long; every time one of them would take a peek, the other would look away, so it wasn’t like they could tell anyway, but they were both walking on eggshells.

Okay, maybe this wasn’t the best idea.

“We should switch positions.”

“Yeah. Totally.”

After a few trial and error poses, they somehow ended up in a rather compromising position. Dipper was reclining on his back, while Mabel was just about sitting in his lap, legs crossed.

Dipper, after a few moments of closing his eyes and thinking of the nastiest, weirdest things he could think of to diffuse the situation, was confident that this wasn’t gonna get any weirder than it already was.

He was wrong.

He opened his eyes, and was greeted with the sight of a beautiful slim back with sharp shoulder blades and soft curves, dimples on the lower portion. Subtle, peachy strawberry-seed freckles dotted her back like constellations, making her pale skin look like the surface of Europa. Dark, wet tendrils of hair plagued the top of the brazenly bare skin as well, adding more contrast and texture to the canvas of her body. 

“Uh, Dip?” A quiet voice quaked, bringing him back down to planet earth.

“What?”

“Move your crotch. Please.”

… Oh. It was only then that Dipper realized the blood flow in his body had changed, leaving a certain part of his pressed against his twin’s buttocks.

“Sorry, Mabes,” he whispered meekly, adjusting himself so that his sudden traitorous erection was free to stand on its own.

“Can’t blame you. I’m pretty hot…” As she said this, although he couldn’t see the expression on her face, he felt a mischievous idea explode from within his sister’s head. As if he could read her mind, and the thoughts were filthy. Mabel slowly but deliberately ground downwards on her brother’s left leg, arching her back and turning her head to watch his silly face, which contorted into a sour expression of frustration and worry.

“S-Stop it, sis,” he insisted, blushing like a fiend and waving his hands in front of him.

“You’re the one who’s got a bone to pick with me,” she winked, glancing down. “Haha. ‘Bone’.” 

“Exactly! Ugh, don’t you get how messed up this really is?!” He groaned in a bitter cry of lamentation. 

That got her to stop her gyrations.

“You know,” she faltered. “It felt kind of right until you mentioned it. Sorry, Dipper, I’m just…” 

She scooted herself to the other end of the tub and slumped like a scolded puppy. It was a drastic change, almost as if she wasa balloon full of helium that had now deflated. Her slender frame was curled inwards, her head visibly shaking back and forth, her face hidden bashfully in her palms.

Was it strange that Dipper felt kind of bad for turning her away? I mean, they had done everything together since they were little; come to think of it, Mabel was the only constant force in his life. Constantly teasing and torturing him in a way that was never malicious, but rather enjoyable. In fact, he kind of liked it. And she was undeniably beautiful. It had to be an aesthetic attraction, though, right?

Could it be that he kind of liked her in general? I mean, he had only walked in on her wearing anything less than a bra and underwear a handful of times, and each time his mind may have gotten stuck in the gutter for longer than it should have, but that’s what happens when you see a girl naked, right?

No. No way. That girl wasn’t just any girl. That girl was the girl that had helped him through everything; breakups, bullying, dark paranormal phenomena. That girl was the girl that had always been there for him, and the one he hoped would always be. Mabel Pines, the handful of rainbow sequins scattered atop the dark, dull fabric of his existence.

_Oh, gross. I’m in love with her, aren’t I?_

He exhaled.

“Listen, Mabel. I—”

“What?” His twin glanced back at him regretfully. “I don’t want you to feel bad because you didn’t wanna do nasty things with your sister.”

“The thing is… I kind of want to, actually. I mean, it seems too convenient. You’re here, I’m here. You’re naked, I’m naked. You look amazing, and I’m… Okay. B-But we’re siblings and it just seems kind of—”

A finger touched his lips. He hadn’t realized that during his tangent, Mabel had turned around. But there she was, mere inches from his face, smiling brightly and tenderly, like a painting of an angel.

“I get it. And it is kinda weird, but you know what they say about weird things?”

“What…?”

“Don’t knock it ‘till you try it.”

She leaned into a deep kiss, nibbling on Dipper’s lower lip like a rabbit on hay. After a short while, Dipper felt bold. He forced his tongue into her mouth, and the moist soft lips that belonged to his sister offered no resistance; instead, her tongue showed up to battle. 

That maaaay have been when things began to heat up more.

“Haha! You’re a really sloppy kisser. Looks like I won this game of tonsil hockey!” The female of the pair giggled, directing her eyes up at the ceiling as a string of drool hung between their mouths.

“Sure, sure, I’ll admit defeat there,” Dipper smirked, rolling his eyes in a similar fashion and breaking the bridge of saliva with his hand and wiping his mouth of the spitty cocktail of delicious peach lipgloss and drool that had been inflicted upon him. Somehow, in this moment, there was something sexy about how sloppy and disgusting this exchange was. So he leaned over her and unplugged the bathtub drain, causing the warm water to begin flowing out. “But these Olympics are just beginning, sis.”

“A sexy one-liner? I like i— Ooh,”

She was forced to stop dead in the middle of her compliment and deteriorate her thoughts into a random quiver as curious fingers traced up and down her back, leaving sensual words in a language that didn’t exist in the realm of sound. She felt a gentle bite tickle the center of her breast. 

Which was when she probably lost all of her inhibitions. Forever. Because this was so worth it, she didn’t care how many laws she was breaking, whether they were the laws of nature or the laws of police.

Meanwhile, a tornado of thoughts raced through the other twin’s head. And he was trying his best to ignore all of them, focusing only on pleasing his favorite girl in the world, even though he had no idea how. He nervously swirled his tongue lower and lower on her soft torso until he ended up near a spot he never thought he would be.

“Uh, may I?” He inquired, gazing up at Mabel eagerly. “I kinda want to try something, if it’s okay…”

“Aw, Dipper. Do you even need to ask?”

 _Okay, man_ , he thought to himself, staring intently at what he was currently viewing as an opponent. _Remember what you read on the Internet._

He began to caress the soft pink slit with his tongue, moving it in the formation of letters of the alphabet in order. Not too spontaneous, but it seemed to be working. Mabel’s body trembled as she reached down to clench fistfuls of her brother’s damp wavy hair. The way he was using his mouth, the way he had began to operate her clit by teasing it with his thumb… Damn, where was he learning this stuff?

“H-Have you done this before?” She panted, secretly afraid of the answer. He didn’t answer by speaking; with one of his fingers, he traced the word ‘no’ on her thigh before moving his hand up to squeeze her buttocks. And she was loving it. In fact, it sort of rocked. Knowing that Dipper had this skill and that she was the only girl he had used it on this far was enough to… Enough to…

“Ahhhn!”

Enough to do that, somehow. Her entire body tensed up as she felt her shoulder blades nearly touch each other, her grip on her brother’s hair tightening as her knuckles turned white, her brain almost following suit.

She felt her brother’s locks slip out of her hands as he sat back up, admiring his handiwork.

“So, Mabes. That was, uh, fast. How was it?” He flashed a wry smile at her glowing, dazed face, secretly eying her rising and falling chest.

“Darn. You made me feel really tired… Sorry, but I don’t think I can follow something like that.”

“It’s cool, though, I swear. I mean, making you feel good was sort of enough for me.” He blushed and scratched his stubbly chin, lying just a little; he was still very much aroused, but if she was done for the night, then so was he. Besides, the self-service thing was never really that hard, and he was used to it anyway.

Mabel draped her arms around her brother sleepily, hooked her legs  
around his body, and whispered into his ear. 

“I owe you one, bro-bro. Could you carry me to bed?”

“No problem, sis,” he replied tenderly, feeling a little bit weary himself. After all, it was about one in the morning and they had school in a few hours. “No problem.”


End file.
